This invention relates to disposable composites, in particular, to those composites which are insensitive to surface moisture, but which are easily disintegrated upon their immersion in an aqueous liquid.
Absorbent articles, such as disposable diapers and sanitary napkins, generally are constructed such that some portion of the article, usually the backing or liner, is a liquid repellent material. This repellent material is desired to minimize or prevent the exudation of the absorbed liquid from the article and to obtain lateral spreading of the absorbed liquid so that the absorbing capacity of the product may be more fully utilized. Liquid repellent materials commonly used heretofore include sheets and films of plastic materials, such as polyethylene films and the like. See, for example, U.S. Pat. Nos. 3,528,421 and 3,804,092.
Due to the nature of their use, it is hygienically undesirable to store the used articles with other refuse for commercial disposal. While disposal of such articles by flushing would be more convenient, the liquid repellent material, which normally does not disintegrate in water, tends to plug toilets and sewer pipes. Accordingly, it is necessary, although undesirable, to separate the repellent material from the article prior to flushing.
Moreover, the packaging in which the disposable articles are delivered are generally made from water-resistant materials. Water resistivity is necessary to prevent the degradation of the packaging from environmental conditions and to protect the disposable articles therein. Although this packaging is safely stored with other refuse for commercial disposal, they often are more conveniently flushed in the toilet with the discarded disposable article, thereby causing plugged drains and toilets.
Heretofore, several methods have been employed to overcome these deficiencies. In one conventional application, various water-dispersible materials are treated with a hydrophobic material to impart the desirable water-resistance properties thereto. For example, U.S. Pat. No. 3,510,587 discloses a disposable diaper having a backing of porous tissue, which has no wet strength, coated with a hydrophobic material such as oil, wax or resin. Similarly, U.S. Pat. No. 3,559,650 discloses a flush-disposable sanitary napkin having a backing of a water-disintegrating material coated on the side exposed to the absorbed fluid with a thin, flexible continuous layer of water-resistant material such as a greasy or oily material. In both instances, the water-resistant coating prevents the absorbed fluid from contacting the water-disintegrating material, thereby maintaining its integrity. Unfortunately, upon disposal in a toilet, the water-resistant materials are not disintegrated, thereby tending to cause the plugging of drains and toilets.
U.S. Pat. No. 3,350,592 proposes a method wherein the outer layer of a sanitary napkin is prepared from fibers or algenic acid and insoluble salts thereof, which are normally insoluble in water. When the napkin is discarded after use, a chemical such as sodium carbonate, is added to the water which changes the fibers to a soluble form by ion exchange. Although this method provides easy flushability of the napkin, the necessity of adding a chemical to the toilet following each use creates an undesirable inconvenience to the user.
In view of the stated deficiencies of the prior art, it remains highly desirable to provide a water-resistant material which degrades or otherwise disintegrates rapidly upon immersion in water, thereby facilitating flushability, but which retains its structural integrity until disposal is desired.